A flash memory, a non-volatile memory semiconductor which can electrically erase or program data, has an advantage of both a RAM that can freely record and erase data and a ROM that can maintain recorded data without power supply. The flash memory is used in many applications, such as a digital camera, PDA, MP3 player, portable phone, portable storing device, and the like.
The flash memory is composed of a plurality of blocks, and each of the plurality of blocks includes a plurality of pages.
In the flash memory, data is programmed in page units. That is, when a program function is performed, data may be sequentially recorded in the pages existing in the flash memory. Also, the data is erased in block units due to an increased complexity of a design, a general problem occurring when the flash memory is actually implemented, and the like. For example, when a single block includes two or more pages, a general flash memory may perform an erase function with respect to the entire single block (the two or more pages), but the general flash memory may not sequentially perform the erase function with respect to one page of the two or more pages.
Also, the flash memory has a limitation that in-place update is impossible. That is, when data recorded in a page A is required to be updated, updated data may not be programmed to the page A again and may be required to be programmed to a page B.
In this instance, when a number of updates of the data increase, pages used in the past become invalid pages. Accordingly, to effectively use the flash memory, it is required to properly collect the invalid pages and initialize them to make initialized blocks. A scheme used in properly collecting and initializing the invalid pages is referred to as a ‘block recycling scheme’.